vars: Make test array quotifying more robust
vars: Make test array quotifying more robust

Turned out it wasn't just Bash 3.x that did this; Travis builds on Linux
running Bash 4.2.25(1)-release were also quotifying array declarations.
This new condition makes the decision to quotify or not more robust and
not so version-specific.

See the following build logs (and also check out how
`assert_lines_equal` made this so easy to diagnose!):

  https://travis-ci.org/mbland/go-script-bash/builds/179126769
  https://travis-ci.org/mbland/go-script-bash/builds/179127585

mbland/go-script-bash